在Golang画一个矩形？ [英] Draw a rectangle in Golang?
问题描述
我想绘制一个带有几个线宽的Go的唯一方法，矩形和条形码，生成并输出PNG / PDF。 标准Go库不提供原始绘图或绘画功能。 b
$ b
它提供的是颜色模型（， JPEG ， PNG ，以及开箱即用的其他格式支持：< a href =http://godoc.org/golang.org/x/image/bmp =noreferrer> BMP ， RIFF ， TIFF ，甚至 WEBP （仅限阅读器/解码器）。
尽管标准库不提供支持，但在图像上绘制线条和矩形相当容易。给定一个 img 图像，它支持使用方法更改像素： Set（x，y int，c color.Color）（例如 image.RGBA 对我们来说是完美的）和类型 col > color.Color ：
// HLine draws水平线
func HLine（x1，y，x2 int）{
for; x1 <= x2; x1 ++ {
img.Set（x1，y，col）
}
}
// VLine绘制一条虚线
func VLine（x， y1，y2 int）{
for; y1 <= y2; y1 ++ {
img.Set（x，y1，col）
}
}
// Rect用HLine（）和VLine（）绘制一个矩形
func Rect（x1，y1，x2，y2 int）{
HLine（x1，y1，x2）
HLine（x1，y2，x2）
VLine（x1，y1，y2 ）
VLine（x2，y1，y2）
}
这里的函数是一个可运行的示例程序，它绘制一条线和一个矩形并将图像保存到 .png 文件中：
<
image/
image/
image/
image/
var img = image.NewRGBA（image.Rect（0，0，100，100））
var col color.Color
func main（）{
col = color.RGBA {255,0,0,255} // Red
HLine（10,20,80）
col = color.RGBA {0,255,0,255 } //绿色
Rect（10，10，80，50）
$ bf，err：= os.Create（draw.png）
if err！= nil {
panic（err）
}
推迟f.Close（）
png.Encode （f，img）
}
如果您想绘制文字，您可以使用执行FreeType 。另外检查这个问题的简单介绍在图像上绘制字符串：如何在Go中为图片添加简单的文本标签？
如果您需要高级和更复杂的绘图功能， 提供了许多外部库，例如：
http://github.com/llgcode/draw2d/
Is the only way to draw a shape in Go with some line width to do it with primitives pixel by pixel?
I want to draw a label with a few rectangles and barcodes, generate and output a PNG/PDF.
The standard Go library does not provide primitive drawing or painting capabilities.
What it provides is models for colors (image/color package) and an Image interface with several implementations (image package). The blog post The Go Image package is a good introduction to this.
It also provides a capability to combine images (e.g. draw them on each other) with different operations in the image/draw package. This can be used to a lot more than it sounds at first. There is a nice blog article about the image/draw package which showcases some of its potential: The Go image/draw package
Another example is the open-source game Gopher's Labyrinth (disclosure: I'm the author) which has a graphical interface and it uses nothing else just the standard Go library to assemble its view.
It's open source, check out its sources how it is done. It has a scrollable game view with moving images/animations in it.
The standard library also supports reading and writing common image formats like GIF, JPEG, PNG, and support for other formats are available out of the box: BMP, RIFF, TIFF and even WEBP (only a reader/decoder).
Although support is not given by the standard library, it is fairly easy to draw lines and rectangles on an image. Given an img image which supports changing a pixel with a method: Set(x, y int, c color.Color) (for example image.RGBA is perfect for us) and a col of type color.Color:
// HLine draws a horizontal line
func HLine(x1, y, x2 int) {
for ; x1 <= x2; x1++ {
img.Set(x1, y, col)
}
}
// VLine draws a veritcal line
func VLine(x, y1, y2 int) {
for ; y1 <= y2; y1++ {
img.Set(x, y1, col)
}
}
// Rect draws a rectangle utilizing HLine() and VLine()
func Rect(x1, y1, x2, y2 int) {
HLine(x1, y1, x2)
HLine(x1, y2, x2)
VLine(x1, y1, y2)
VLine(x2, y1, y2)
}
Using these simple functions here is a runnable example program which draws a line and a rectangle and saves the image into a .png file:
import (
"image"
"image/color"
"image/png"
"os"
)
var img = image.NewRGBA(image.Rect(0, 0, 100, 100))
var col color.Color
func main() {
col = color.RGBA{255, 0, 0, 255} // Red
HLine(10, 20, 80)
col = color.RGBA{0, 255, 0, 255} // Green
Rect(10, 10, 80, 50)
f, err := os.Create("draw.png")
if err != nil {
panic(err)
}
defer f.Close()
png.Encode(f, img)
}
If you want to draw texts, you can use the Go implementation of FreeType. Also check out this question for a simple introduction to drawing strings on images: How to add a simple text label to an image in Go?
If you want advanced and more complex drawing capabilities, there are also many external libraries available, for example:
http://github.com/llgcode/draw2d/
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